ABSTRACT The threat of radiological and nuclear accidents or attacks demands effective radiation medical countermeasures (MCM) able to mitigate and treat the effects of exposure to ionizing radiations. Hematopoietic acute radiation syndrome (HRAS) and cutaneous radiation syndrome (CRS) pose severe, life-threatening risks to exposed individuals. Currently no effective radio-mitigator (to be administered after radiation exposure but prior to tissue toxicity manifestation) or radio-therapeutic (to be administered after tissue toxicity manifestation) has yet received FDA approval. Fibroplate, Inc. developed Fibrinoplate-S (FPS), an intravenous injectable solution of Fibrinogen-coated Albumin nano-Spheres originally developed to augment hemostatic functions in multiple clinical settings. Preliminary studies conducted on irradiated rodents suggested that FAS administered after ionizing radiation exposure has a unique potential as a multi-valent MCM against radiations. In particular, it was demonstrated that FPS has prophylactic properties against Radiation-induced Skin Injuries (RSI). During the SBIR Phase I project, a preclinical feasibility study in rats was performed to demonstrate FPS? efficacy as a therapeutic treatment for RSI. Several objectives were accomplished: 1) The efficacy of FPS as both prophylactic and therapeutic treatment for RSI was demonstrated. 2) An FPS-induced stem cells mobilization towards the lesion was observed. 3) The efficacy of FPS as a mitigator for neutropenia and thrombocytopenia was confirmed. 4) A regulatory effect of FPS on the cytokine profile was discovered. Results obtained in Phase I represent the perfect starting point for this SBIR Phase II project, where additional preclinical studies will be performed and used to complete an IND submission package to the FDA, to pursue FDA approval according to the Animal Efficacy Rule. In this SBIR Phase II project, Fibroplate aims at: i) Demonstrate FPS efficacy as a therapeutic treatment for RSI in minipigs, as a second animal model. ii) Assess FPS toxicology profile in rats, iii) Assess FPS stability and shelf-life, iv) Scale-up current manufacturing process to reach production volumes sufficient to sustain the clinical development. Obtaining FDA approval for FPS will pave the way for its inclusion in the Strategic National Stockpile as MCM for radiological/nuclear emergencies. 1